1. Field of the Invention
The present invention relates to a sheet-fed scanner having a bent linking member, and more particularly to a sheet-fed scanner using a bent linking member to distribute an exerted force and to improve the scan image quality.
2. Related Art
When a conventional sheet-fed scanner scans an original sheet, especially a card, with its suspended scan assembly, the original sheet lifts up the suspended scan assembly by a stroke determined by the thickness of the original sheet. For example, when a cardboard, such as a credit card, enters the sheet passageway and contacts the rollers at the sheet-input end of the scan assembly, the scan assembly is inclined with its front-end lifted up to accommodate the cardboard. When the rollers at both of the sheet-input end and the sheet-output end contact the cardboard, the scan assembly restores the horizontal state. When the cardboard leaves the nip between the rollers at the sheet-input end, the scan assembly is inclined again, where at this time its rear-end is lifted up by the cardboard, since the cardboard is still in contact with the rollers at the sheet-output end. The motion of the scan assembly from one inclined state to the horizontal state, and then to another inclined state may be referred to as the seesaw motion, which causes the seesaw effect.
When the scan assembly is using, for example, a contact type image sensor (CIS), its depth of field is short and its scan precision is low. The seesaw effect will seriously affect the quality of the image outputted from the CIS. In addition, the thicker the original sheet is, the greater is the image shock which deteriorates the scan image quality.